1. Field of the Invention
The present invention relates to a stage apparatus suitable for use in high-precision processing, such as semiconductor lithography, and to an exposure apparatus having the stage apparatus.
2. Description of the Related Art
Representative known exposure apparatuses for use in fabrication of semiconductor devices and the like are a step-and-repeat exposure apparatus (also called a stepper) and a step-and-scan exposure apparatus (also called a scanner). In the step-and-repeat exposure apparatus, a pattern on an original plate (reticle or mask) is sequentially transferred onto a plurality of areas on a substrate (wafer of glass substrate) by exposure through a projection optical system while moving the substrate step by step. In the step-and-scan exposure apparatus, step movement and scanning exposure are repeated to expose and transfer a pattern onto a plurality of areas on a substrate. In particular, the step-and-scan exposure apparatus uses only the portion of a projection optical system that is close to the optical axis by limiting an exposure light beam with a slit, and hence can expose fine patterns with high accuracy at a wide field angle.
These exposure apparatuses have stage apparatuses (a wafer stage and a reticle stage) for moving a wafer and a reticle at high speed for positioning. However, the high-speed and high-precision positioning of the stages may be hindered by thrust variations of a multiphase linear motor, disturbances due to vibration caused by switching of a multiphase linear motor coil during the driving of the stages (hereinafter generically named “cogging”), or disturbances transmitted from mounted components such as tubes and cables.
Some suggestions have been made in order to overcome thrust variations of the multiphase linear motor, cogging, and disturbances due to mounted components. For example, Japanese Patent Laid-Open No. 9-149672 discloses an apparatus that improves accuracy by making a table for correcting position errors with respect to desired values based on the result of one scanning operation of a stage. In other known methods, the disturbances of a rough-motion stage that has a long stroke are generally prevented by using a fine-motion stage mounted on a top plate and a multiphase linear motor.
In the control method described in the Japanese Patent Laid-Open application for reducing cogging, however, frequency increases with the stage speed, causing disturbances. Moreover, the amplitude level also increases with stage speed, thereby decreasing stage accuracy. In the other known methods, the fine-motion mechanism that must be constructed on the top plate complicates the structure of the stage and increases the mass of the stage. As a result, control performance is reduced and heat generation increases.
In methods using a fine-motion stage mounted on a top plate, the long-stroke stage is driven by sequentially energizing coils; during scanning exposure, the stage control accuracy is decreased due to torque ripple caused by switching the coils. The stage control accuracy is also decreased by resistance and disturbances due to the cables and tubes connected to the stage during scanning exposure.